Exterior Comfort Board continuing from below grade, up the sheathing – GreenBuildingAdvisor

Replies

1. Expert Member

   MALCOLM TAYLOR | Mar 16, 2026 11:56am | #1

   Billy,

   You can, but it presupposes your stem-walls and the framing above are going to align very closely. If I were doing it I’d have a drip-flashing, and whatever material you are planning to use as a covering for the mineral wool stopping at the top of the stem-wall – which would also provide a barrier against infestations moving upwards. You can still use a foot of mineral wool above that before starting the foam.

2. GBA Editor

   RANDY WILLIAMS | Mar 16, 2026 05:03pm | #2

   As Malcolm said, it can be done that way. This is from a project we worked on a couple years ago. The wall insulation planed out with the foundation insulation. 3-in on the foundation, 2 1/2-in. on the wall plus the 1/2-in osb. We added the drip cap even though everything was in the same plane.

   

3. 

   jhwehrli | Mar 16, 2026 10:10pm | #3

   Yes, have done this detail but the precautions that @MALCOLM TAYLOR added are a must-do. We also did a dimple mat behind the Comfortboard (and of course foundation waterproofing) so that any water infiltrating against the insulation had a plane to run down.